package com.atguigu.tree;

import java.util.TreeMap;

public class Trie {

    private static final class Node{
        public boolean isWord;
        public TreeMap<Character,Node>next;
        public Node(boolean isWord){
            this.isWord=isWord;
            next=new TreeMap<>();
        }
        public Node(){
            this(false);
        }
    }
    private Node root;
    private int size;
    public Trie(){
        root= new Node();
        size=0;
    }
    //获取Trie中存储的单词的数量
    public int getSize(){
        return size;
    }
    //向Trie中添加元素，非递归算法
    public void add(String word){
        Node cur=root;
        for (int i = 0; i < word.length(); i++) {
            char c=word.charAt(i);
            if(cur.next.get(c)==null) {
                cur.next.put(c, new Node());
            }
            cur=cur.next.get(c);
        }
        if(!cur.isWord){
            cur.isWord=true;
            size++;
        }
    }
    //向字典树中添加元素，递归算法
    public void addR(String word){
        addR(root, 0,word);
    }
    private void addR(Node cur, int index, String word){
        if(index == word.length()){
            if(!cur.isWord){
                cur.isWord = true;
            }
            return;
        }
        char c = word.charAt(index);
        if(cur.next.get(c) == null){
            cur.next.put(c, new Node());
            size++;
        }
        addR(cur.next.get(c), index + 1, word);
    }
    //查询单词是否在Trie中
    public boolean contains(String word){
        Node cur=root;
        for (int i = 0; i < word.length(); i++) {
            char c=word.charAt(i);
            if(cur.next.get(c)==null){
                return false;
            }
            cur=cur.next.get(c);
        }
        return cur.isWord;
    }
    //查询是否在Trie中有单词以prefix为前缀
    public boolean isPrefix(String prefix){
        Node cur=root;
        for (int i = 0; i < prefix.length(); i++) {
            char c=prefix.charAt(i);
            if(cur.next.get(c)==null){
                return false;
            }
            cur=cur.next.get(c);
        }
        return false;
    }
}
